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B7x: a widely expressed B7 family member that inhibits T cell activation.

ABSTRACT: B7 family proteins provide costimulatory signals that regulate T cell responses. Here we report the third set of B7 family-related T cell inhibitory molecules with the identification of a homolog of the B7 family, B7x. It is expressed in immune cells, nonlymphoid tissues, and some tumor cell lines. B7x inhibits cell-cycle progression, proliferation, and cytokine production of both CD4+ and CD8+ T cells. B7x binds a receptor that is expressed on activated, but not resting T cells that is distinct from known CD28 family members. Its receptor may be a recently identified inhibitory molecule, B and T lymphocyte attenuator. These studies identify a costimulatory pathway that may have a unique function in downregulation of tissue-specific autoimmunity and antitumor responses.

SUBMITTER: Zang X

PROVIDER: S-EPMC193571 | biostudies-literature | 2003 Sep

REPOSITORIES: biostudies-literature

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B7x: a widely expressed B7 family member that inhibits T cell activation.

Zang Xingxing X Loke P'ng P Kim Jayon J Murphy Kenneth K Waitz Rebecca R Allison James P JP

Proceedings of the National Academy of Sciences of the United States of America 20030814 18

B7 family proteins provide costimulatory signals that regulate T cell responses. Here we report the third set of B7 family-related T cell inhibitory molecules with the identification of a homolog of the B7 family, B7x. It is expressed in immune cells, nonlymphoid tissues, and some tumor cell lines. B7x inhibits cell-cycle progression, proliferation, and cytokine production of both CD4+ and CD8+ T cells. B7x binds a receptor that is expressed on activated, but not resting T cells that is distinct ...[more]

PMID: 12920180

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Project description:PurposeHHLA2 (B7H7/B7-H5/B7y) is a newly identified B7 family member that regulates human T-cell functions. However, its protein expression in human organs and significance in human diseases are unknown. The objective of this study was to analyze HHLA2 protein expression in normal human tissues and cancers, as well as its prognostic significance, to explore mechanisms regulating HHLA2 expression, and to identify candidate HHLA2 receptors.Experimental designAn immunohistochemistry protocol and a flow cytometry assay with newly generated monoclonal antibodies were developed to examine HHLA2 protein. HHLA2 gene copy-number variation was analyzed from cancer genomic data. The combination of bioinformatics analysis and immunologic approaches was established to explore HHLA2 receptors.ResultsHHLA2 protein was detected in trophoblastic cells of the placenta and the epithelium of gut, kidney, gallbladder, and breast, but not in most other organs. In contrast, HHLA2 protein was widely expressed in human cancers from the breast, lung, thyroid, melanoma, pancreas, ovary, liver, bladder, colon, prostate, kidney, and esophagus. In a cohort of 50 patients with stage I-III triple-negative breast cancer, 56% of patients had aberrant expression of HHLA2 on their tumors, and high HHLA2 expression was significantly associated with regional lymph node metastasis and stage. The Cancer Genome Atlas revealed that HHLA2 copy-number gains were present in 29% of basal breast cancers, providing a potential mechanism for increased HHLA2 protein expression in breast cancer. Finally, Transmembrane and Immunoglobulin Domain Containing 2 (TMIGD2) was identified as one of the receptors for HHLA2.ConclusionsWide expression of HHLA2 in human malignancies, together with its association with poor prognostic factors and its T-cell coinhibitory capability, suggests that the HHLA2 pathway represents a novel immunosuppressive mechanism within the tumor microenvironment and an attractive target for human cancer therapy.

Dataset Information

B7x: a widely expressed B7 family member that inhibits T cell activation.

Publications

B7x: a widely expressed B7 family member that inhibits T cell activation.

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